UBRARY 
STATE  PLANT  BOARD 


Issued  November  25,  1910. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU   OF   ENTOMOLOGY— CIRCULAR   No.  125. 

L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


INSECTS  WHICH  KILL  FOREST  TREES: 

CHARACTER  AND  EXTENT  OF  THEIR  DEPREDATIONS 
AND  METHODS  OF  CONTROL. 


A.  D.  HOPKINS, 

In  Charge  of  Forest  Insect  Investigations. 


G4136°— Cir.  125—10 

WASHINGTON    :  GOVERNMENT  PRINTING  OFFICE   :   1910 


BUREAU  OF  ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  (Jh'wf  of  Bureau. 

C.  L.  Marlatt,  Afisistant  Entomologist  and  Acting  Chief  in  Ahsnicc  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 
W.  F.  Tastet,  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  insect  investigations, 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

F.  M.  Webster,  m  charge  of  cereal  and  forage  insect  investigations. 

A.  L.  QuAiNTANCE,  in  charge  of  deciduous  fruit  insect  investigations. 

E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  work. 
RoLLA  P.  Currie,  in  charge  of  editorial  icork. 

Mabel  Colcord,  librarian. 

Forest  Insect  Investigations. 

A.  D.  Hopkins,  in  charge. 

H.  E.  Burke,  J.  L.  Webb,  Jose*^  Brunner,  S.  A.  Rouwer,  T.  K.  Snvdkr,  W.  D. 

Edmonston,  agents  and  experts. 
Mary  E.  Faunce,  preparator. 

William  Middleton,  Mary  C.  Johnson,  student  assistants. 
[Cir.  125] 
n 


Circular  No.  125.  Issued  November  25,  1910. 

United  States  Department  of  Agriculture, 

BUREAU   OF  ENTOMOLOGY. 
L.  O.  HOWARD,  Entomologist  and  Chief  of  Bureau. 


INSECTS  WHICH  KILL  FOREST  TREES:  CHARACTER 
AND  EXTENT  OF  THEIR  DEPREDATIONS  AND  METH- 
ODS OF  CONTROL." 

By  A,  D.  Hopkins, 
In  Charge  of  Forest  Insect  Investigations. 

It  has  been  conclusively  demonstrated  that  certain  species  of  insects 
are  the  direct  or  primar}^  cause  of  the  death  of  forest  trees  of  all 
ages,  and  that  from  time  to  time  they  multiply  to  such  an  alarming 
extent  that  their  depredations  assume  the  character  of  a  destructive 
invasion,  which  results  in  the  death  of  a  large  percentage  of  the  best 
timber  over  thousands  of  square  miles. 

There  are  many  species  of  barkbeetles  which  prefer  to  attack 
matured  and  healthy  trees,  and  there  are  many  examples  of  whole 
forests  of  century-old  trees  that  have  perished  from  the  girdling  effect 
of  the  mines  of  the  beetles,  which  are  extended  in  all  directions 
through  the  inner  living  bark  on  the  main  trunks  of  the  trees. 
Indeed,  we  find  among  these  bark-boring  beetles  the  most  destructive 
insect  enemies  of  North  American  forests.  Some  notable  examples 
of  the  depredations  of  these  barkbeetles  are  given  below. 

The  southern  pine  beetle. — In  1890-1892  a  destructive  invasion  of 
the  southern  pine  beetle  extended  from  the  western  border  of  AYest 
Virginia  through  Maryland  and  Virginia  into  the  District  of  Colum- 
bia, northward  into  southern  Pennsjdvania,  and  southward  into  North 
Carolina.  In  this  area,  aggregating  over  75,000  square  miles,  a  very 
large  percentage  of  the  mature  and  small  trees  of  the  various  species 
of  pine  and  spruce  was  killed  by  this  beetle.  In  many  places  in  West 
Virginia  and  Virginia  nearly  all  the  pine  trees  of  all  sizes  on  thou- 
sands of  acres  were  killed,  while  shade  and  ornamental  trees  within 
the  same  area  suffered  the  same  as  those  in  the  forest.     Since  1902 

«  Revised  extracts  from  Bulletin  No.  58,  Part  V,  Bureau  of  Entomology,  U.  S. 
Department  of  Agriculture,  1909. 

[Cir.  125]  1 


2  INSECTS    WHICH   KILL  FOEEST   TREES. 

this  barkbeetle  has  been  more  or  less  active  in  the  Southern  States 
from  Virginia  to  Texas,  and  in  some  localities  and  during  certain 
years  it  has  killed  a  large  amount  of  timber.  Records  of  extensive 
destruction  of  timber  in  the  Southern  States  are  found  dating  back 
to  the  early  part  of  the  nineteenth  centuiy.  This  species  may  be 
considered  one  of  the  most  dangerous  insect  enemies  of  southeastern 
conifers  and,  therefore,  a  constant  menace  to  the  pine  forests  of  the 
Southern  States. 

The  eastern  spruce  heetle. — During  the  period  between  1818.  and 
1900  there  were  several  outbreaks  of  the  eastern  spruce  beetle  in  the 
spruce  forests  of  New  York,  New  England,  and  southeastern  Canada. 
This  species  caused  the  death  of  a  very  large  percentage  of  the  ma- 
ture spruce  over  an  area  of  thousands  of  square  miles.  In  the  aggre- 
gate many  billions  of  feet  of  the  best  timber  were  destroyed.  The 
larger  areas  of  this  dead  timber  furnished  fuel  for  devastating  for- 
est fires,  with  the  result  that  in  most  cases  there  was  a  total  loss. 

The  Engelmann  spruce  heetle. — The  Engelmann  spruce  beetle, 
with  habits  similar  to  the  eastern  spruce  beetle,  has  from  time  to  time 
during  the  past  fifty  years  caused  widespread  devastations  in  the 
Rocky  Mountain  region  to  forests  of  Engelmann  spruce,  in  some  sec- 
tions killing  from  75  to  90  per  cent  of  the  timber  of  merchantable  size. 

The  Black  Hills  heetle. — One  of  the  most  striking  examples  of  the 
destructive  powers  of  an  insect  enemy  of  forest  trees  is  found  in  the 
Black  Hills  National  Forest  of  South  Dakota,  where  during  the  past 
ten  years  a  large  percentage  of  the  merchantable  timber  of  the  entire 
forest  has  been  killed  by  the  Black  Hills  beetle.  It  is  estimated  that 
more  than  a  billion  feet  of  timber  have  been  destroyed  in  this  forest 
as  the  direct  result  of  the  work  of  this  beetle.  This  destructive 
enemy  of  the  western  pine  is  distributed  throughout  the  forests  of 
the  middle  and  southern  Rocky  Mountains  region,  where,  within 
recent  years,  it  has  been  found  that  in  areas  of  greater  or  less  extent 
from  10  to  80  per  cent  of  the  trees  have  been  killed  by  it. 

The  mountain  pine  heetle  and  the  western  pine  hectic. — The  sugar 
pine,  silver  pine,  western  yellow  pine,  and  lodgepole  pine  of  the 
region  north  of  Colorado  and  Utah,  westward  to  the  Cascades,  and 
southward  through  the  Sierra  Nevadas  are  attacked  by  the  mountain 
pine  beetle  and  the  western  pine  beetle,  and,  as  a  direct  consequence, 
billions  of  feet  of  the  timber  have  died.  In  one  locality  in  northeast- 
ern Oregon  it  is  estimated  that  90  to  95  per  cent  of  the  timber  in  a 
dense  stand  of  lodgepole  pine  covering  an  area  of  100,000  acres  has 
been  killed  within  the  past  three  years  by  the  mountain  pine  beetle. 
Through  many  sections  of  the  sugar-j)ine  districts  of  Oregon  and 
California,  as  the  result  of  attacks  by  this  same  destructive  barkbeetle 
a  considerable  percentage  of  the  largest  and  best  trees  is  dead. 

IClr.  ILT.I 


INSECTS    WHICH    KILL   FOREST   TREES.  3 

The  Douglas  fr  beetle. — The  Douglas  fir  throughout  the  region 
of  the  Rocky  Mountains  from  southern  New  Mexico  to  British  Co- 
lumbia has  suffered  severely  from  the  ravages  of  the  Douglas  fir 
beetle,  with  the  result  that  a  large  percentage  of  dead  timber  is  found, 
much  of  which  will  be  a  total  loss. 

Three  other  species  of  beetles,  having  destructive  habits  similar 
to  those  above  mentioned,  depredate  on  the  pines  of  Xew  ^lexico  and 
Arizona,  and  still  another  has  contributed  greatly  to  the  destruction 
of  the  larch  throughout  the  northeastern  United  States  and  south- 
eastern Canada. 

The  hickory  harhheetle. — Within  the  past  ten  years  the  hickory 
barkbeetle  has  caused  the  destruction  of  an  enormous  amount  of 
hickory  timber  throughout  the  northern  tier  of  States  from  Wiscon- 
sin to  Vermont  and  southward  through  the  eastern  Atlantic  States 
and  into  the  Southern  States  as  far  as  central  Georgia. 

2' he  larch  icorm. — There  are  also  many  examples  of  Avidespread 
depredations  chargeable  to  insects  which  defoliate  the  trees,  thus 
contributing  to  their  death.  Notable  among  these  are  the  depreda- 
tions by  the  larch  worm,  which,  during  several  extensive  outbreaks 
since  1880,  has  killed  from  50  to  100  per  cent  of  the  mature  larch 
over  vast  areas  in  the  northeastern  United  States  and  southeastern 
Canada.  It  is  evident  that  the  amount  of  merchantable-sized  timber 
that  has  died  as  the  result  of  defoliation  by  this  insect  will  aggregate 
many  billions  of  feet. 

CONTROL  OF    BARKBEETLES    WHICH    KILL   TREES. 

The  barkbeetles  which  kill  trees  attack  the  bark  on  the  trunk  and 
destroy  the  life  of  the  tree  by  extending  their  burrows  or  galleries  in 
all  directions  through  the  inner  living  bark.  The  broods  of  young 
grubs  or  larvae  develop  within  the  inner  bark,  on  which  they  feed. 
Those  of  some  species  develop  to  the  adult  stage  within  the  inner  bark 
and  are  exposed  when  the  bark  is  removed,  while  those  of  other 
species  transform  to  the  adults  in  the  outer  corky  bark  and  the  larva? 
are  not  exposed  when  the  bark  is  removed.  Some  species  have  two 
or  more  generations  in  a  season  or  annually,  while  others  have  but 
one,  and  in  a  few  species  it  requires  two  years  for  a  single  generation 
to  develop. 

The  barkbeetles  of  the  genus  Dendroctonus  represent  the  most 
destructive  enemies  of  the  principal  coniferous  tree  species  of  Ameri- 
can forests,  and  at  the  same  time  are  among  the  easiest  of  control. 
The  general  requisites  for  success  are  embodied  in  the  following  rules : 

{a)  Give  prompt  attention  to  the  first  evidence  of  a  destructive 
outbreak,  as  indicated  by  an  abnormal  percentage  of  yellow  or  red 
topped  dying  trees,  and  especially  when  such  trees  occur  in  groups  of 
ten  or  more  or  cover  large  areas;   (6)   secure  authentic  determination 

[Cir.  125] 


4  INSECTS   WHICH   KILL  FOREST   TREES. 

of  the  particular  species  of  insect  responsible  for  the  trouble;  and 
(c)  take  prompt  action  toward  its  control  according  to  specific  expert 
advice,  published  or  otherwise,  on  the  best  method  for  the  destruction 
of  the  necessary  75  percent  or  more  of  the  insects  in  the  infested  trees. 
Some  of  the  methods  to  be  adopted  to  meet  the  requirements  of 
various  local  conditions  are  as  follows: 

(1)  Utilize  the  infested  timber  and  burn  the  slabs  during  the 
period  in  which  the  broods  of  the  destructive  beetles  are  in  the  imma- 
ture stages  or  before  the  developed  broods  emerge  from  the  bark ;  or 

(2)  Fell  the  infested  trees  and  remove  the  bark  from  the  main 
trunk  and  burn  the  bark  if  necessary ; "  or 

(3)  Remove  the  infested  bark  from  the  standing  timber  and  burn 
the  bark  when  necessary ; «  or 

(4)  Immerse  the  unbarked  logs  in  ponds,  lakes,  or  streams,  where 
the  bark  will  remain  soaked  long  enough  to  kill  the  insects;  or 

(5)  Remove  the  unbarked  logs  or  products  to  a  localit}^  Avhere 
there  are  no  trees  liable  to  attack  within  a  radius  of  20  miles  or  more. 

Maintaining  Control  of  Barkheetles. 

Future  trouble  of  a  serious  nature  from  barkheetles  which  kill 
trees  can  be  prevented  within  a  given  forest  or  area  of  greater  or  less 
extent  if  an  insect-control  policy  is  adopted  in  connection  with,  or 
independent  of,  a  fire-control  policy  b}^  which  groups  of  dying  trees 
will  receive  similar  prompt  attention  as  that  required  for  the  pre- 
vention or  control  of  forest  fires. 

In  state  and  national  forests. — In  all  forest  reserves  in  which  there 
is  an  organized  force  of  rangers  and  fire  wardens  or  patrols  each 
officer  should  be  furnished  with  instructions  for  the  location  of 
beetle-infested  trees,  and  with  equipment  and  directions  for  taking 
the  necessar}^  action  whenever  the  conditions  demand  or  warrant  it. 

In  private  forests. — Private  forests  should  receive  the  same  atten- 
tion as  public  forests,  but  this  is  often  far  more  difficult  on  account 
of  intervening  forests  where  the  owners  either  can  not  or  will  not 
give  the  matter  the  required  attention.  AVhile  it  may  be  advisable 
to  have  some  laws  to  govern  the  treatment  of  timber  infested  with  a 
dangerous  pest  when  the  owner  refuses  to  take  any  action,  such  a 
law  should  apply  only  to  the  more  extreme  cases  or  as  a  last  resort 
on  authoritative  advice.  It  is  probable  that  in  most  cases  legislation 
will  not  be  necessary,  and  more  ultimate  good  will  result  without 
than  with  strict  laws,  especially  when  it  can  be  made  clear  to  the 


°  If  the  broods  develop  to  adults  in  the  outer  l)ark,  it  must  he  burned  ;  if  they 
develop  in  the  inner  barl<  and  are  expos(Ml  when  the  bark  is  removed,  burning 
is  not  necesstiry.     As  a  rule  the  burning  of  the  tops  to  destroy  the  insects  is 
not  necessary. 
H'lr.  125] 


INSECTS    WHICH    KILL    FOREST    TREES.  5 

owner  that  his  personal  interests  demand  that  he  take  the  proper 
action  and  that,  when  necessary,  his  neighbors  will  render  assistance, 
as  is  done  in  the  case  of  a  forest  fire. 

Inaccessible  areas. — There  are  yet  large  inaccessible  areas  in  the 
East  and  West  where  it  is  not  practicable  or  possible  at  present  to 
control  the  depredations  by  these  beetles  and  which  must  therefore 
be  left  to  the  same  natural  adjustment  that  has  been  going  on  in 
all  forests  from  their  beginning.  While  under  such  natural  control 
much  of  the  older  matured  timber  will  be  lost  it  will  usually  be  re- 
placed by  young  growth,  either  of  the  same  species  of  trees  or  of  a 
different  species,  so  that  under  normal  conditions  the  forest  will  be 
perpetuated ;  but  under  exceptional  conditions  and  combinations  of 
detrimental  influences,  such  as  secondary  insect  enemies,  fire,  and 
drought,  extensive  areas  may  be  completely  denuded,  never  to  be 
reforested  under  natural  conditions.  Therefore  it  will  evidently  not 
be  very  long  before  it  will  pay  to  adopt  insect-control  policies  even  in 
the  areas  that  are  inaccessible  for  profitable  lumbering. 

Examples  of  Successful  Control  of  Barkbeetles. 

The  practicability  of  the  advice  based  on  the  results  of  recent  ento- 
mological investigations  is  demonstrated  by  a  number  of  examples  of 
successful  control  of  depredations  by  destructive  barkbeetles. 

CONTROL  OF  THE  EASTERN  SPRUCE  BEETLE. 

The  control  of  an  alarming  outbreak  of  the  eastern  spruce  beetle 
in  northeastern  Maine  in  1900  and  1901  was  effected  by  the  concentra- 
tion of  regular  logging  operations  into  the  areas  of  infested  timber 
and  placing  the  logs  in  lakes  and  streams  and  driving  them  to  the 
mills  on  the  Androscoggin  River.  Thus,  with  little  or  no  additional 
expense,  there  was  a  saving  to  one  firm,  according  to  its  estimates, 
of  more  than  $100,000. 

CONTKOI.    OF    THE    HICKORY    BARKBEETLE. 

The  complete  control  of  the  hickory  barkbeetle,  which  threatened 
the  total  destruction  of  the  hickory  trees  on  Belle  Isle  Park,  at  Detroit, 
Mich.,  in  190fi,  was  effected  by  felling  and  removing  the  infested  trees 
and  converting  them  into  merchantable  products,  all  without  cost  to 
the  park  conmiission. 

CONTKOI.    OF    THE    HIJACK    HILLS    BEETLE. 

An  extensive  outbreak  of  the  Black  Hills  beetle  in  the  vicinity  of 
Colorado  Springs,  Colo.,  in  1905-G,  which  was  threatening  the  living 
pine  timber  of  the  entire  section,  was  brought  under  control  through 
the  efforts  of  the  private  owners  of  forests  and  those  of  forest  offi- 
cials in  the  adjoining  National   Forests.     It  was  accomplished   by 

[Cir.  12.-1 


6  INSECTS    WHICH    KILL  FOEEST    TREES. 

cutting  aild  barking  about  1.000  beetle-infested  and  beetle-killed  pine 
trees.  The  cost  of  the  operations  was  largely,  if  not  entirely,  coy- 
ered  by  the  utilized  felled  timber,  although  there  was  considerable 
unnecessary  expense  inyohed  through  the  felling  and  barking  of 
trees  from  which  the  beetles  had  emerged  and  from  the  unnecessary 
burning  of  the  bark  and  tops. 

The  successful  control  of  another  serious  outbreak  of  this  beetle,  in 
1906.  on  an  extensive  private  estate  in  southern  Colorado,  was  effected 
through  the  efforts  of  the  owners,  who  had  some  500  infested  trees 
felled  and  barked  within  the  necessary  period  to  destroy  the  broods. 
A  large  percentage,  but  not  all.  of  the  infested  timber  was  thus 
treated.  These  operations  were  so  successful  that  not  a  single  in- 
fested and  dying  tree  could  be  found  when  the  area  was  inspected  in 
1908.  In  this,  as  in  the  other  case,  considerable  unnecessary  expense 
was  involved  in  the  burning  of  the  bark  and  tops,  but  the  value  of 
utilizable  timber  was  probably  more  than  enough  to  pay  all  expenses. 
It  is  evident  that  in  this  case  a  destructive  invasion  was  prevented. 

The  practicability  of  controlling  this  most  destructive  enemy  of  the 
pine  timber  of  the  central  Rocky  Mountain  region,  not  only  without 
ultimate  cost  but  at  a  profit  on  the  oi)erations.  was  demonstrated  on 
a  large  private  estate  and  the  adjoining  Pike  National  Forest  in 
north-central  Colorado.  An  examination  of  the  timber  on  this  estate 
in  the  spring  of  1907.  by  a  ranger  detailed  from  the  Forest  Service  to 
work  under  instructions  from  the  Bureau  of  Entomology,  showed 
that  the  depredations  by  the  beetle  had  been  going  on  for  the  past  ten 
years  or  more  and  had  resulted  in  the  death  of  the  choicest  timber  to 
the  extent  of  more  than  800.000  board  feet.  About  65,000  board  feet 
of  timber  was  found  to  be  infested  by  the  beetle  at  the  time  of  the  ex- 
amination. The  owner  was  notified  by  the  Bureau  of  Entomology 
of  the  dangerous  character  of  the  infestation  and  the  required  action 
for  its  control  was  recommended,  but  no  action  was  taken.  Another 
examination  of  the  property  was  made  in  the  fall  of  1907,  when  it 
was  found  that  the  new  infestation  resulting  from  swarms  of  beetles 
that  had  been  allowed  to  emerge  from  the  old  infested  trees  involved 
nearly  four  times  as  much  timber,  or  i^-tO.OOO  board  feet.  This  alarm- 
ing increase  led  to  the  prompt  adoption  of  the  recommendations 
by  the  owner  and  the  Forest  Service,  and  by  ^lay  of  the  following 
spring  (1908)  the  small  number  of  trees  on  the  National  Forest  was 
cut  and  barked,  to  kill  the  insects  in  the  inner  bark,  and  the  1,000 
trees  on  the  private  estate  were  felled,  the  logs  converted  into  lumber, 
and  the  slabs  burned,  which  accomplished  the  desired  purpose  of  de- 
stroying the  broods  of  the  beetle.  The  owner  realized  a  sufficient 
revenue  from  the  timber  thus  involved  to  cover  all  expenses  and  leave 
a  net  profit  of  over  $1,200.  Examination  of  the  area  in  the  fall  of 
1908  showed  that  this  prompt  and  properly  conducted  effort  to  con- 
[rir.  lunj 


INSECTS   WHICH    KILL   FOREST    TREES.  7 

trol  the  beetle  was  a  complete  success.  Thus  the  average  death  rate 
of  some  100,000  feet  of  timber  annually  during  the  past  ten  or  more 
years  was  reduced  to  a  minimum,  at  a  net  profit  on  the  cost  of  doing  it. 

In  addition  to  infested  trees  disposed  of  by  the  Forest  Service  in 
timber  sales,  165  infested  trees  in  one  section  of  the  Las  Animas 
National  Forest  were  cut  and  barked  in  May  and  June,  1908,  at  a 
direct  cost  of  $177.50.  and  at  the  same  time  a  considerable  amount  of 
infested  timber  was  disposed  of  by  sale  in  the  Wet  Mountains  section 
of  the  San  Isabel  National  Forest.  This  had  a  decided  effect  in 
checking  the  ravages  of  the  beetle  in  both  of  these  forests  and  it  was 
followed  up  in  the  latter  forest  the  next  spring  (1909)  by  the  proper 
disposal  of  over  1,000  infested  trees  by  free  use,  ranger  labor,  and 
direct  expenditure  of  funds  appropriated  by  the  Forest  Service. 
According  to  the  forest  supervisor's  report,  80.7  per  cent  of  the 
infested  trees  were  treated,  ranging  from  70  per  cent  to  92.5  per  cent 
on  the  five  units  of  infestation:  795  trees  were  treated  (535  barked, 
and  2G0  felled  and  bark  scorched)  at  the  expense  of  the  Forest  Serv- 
ice, including  salary  and  expenses  of  rangers.  The  cost  per  tree  was 
about  60  cents  for  felling  and  barking,  and  ranged  from  52  to  78 
cents  for  felling  and  scorching  the  bark  on  the  infested  trunks.  The 
average  cost  per  tree  was  68.2  cents.  Six  hundred  and  twenty-six 
trees  were  treated  by  temporary  labor,  at  an  average  cost  of  61  cents 
per  tree  under  contract  at  $1.50  to  $2  per  hundred  feet  in  length  of 
trunk  peeled.  The  same  rate  was  allowed  for  scorching  the  infested 
bark  instead  of  removing  it.  Two  hundred  and  seventy-five  trees 
were  treated  under  administrative  use  without  cost  to  the  Forest 
Service. 

In  September,  1909,  a  very  thorough  examination  was  made  of 
the  timber  in  and  adjacent  to  the  areas  involved  in  the  control  opera- 
tions, and  it  was  found  that  the  thorough,  prompt,  and  proper  manner 
in  which  the  instructions  of  the  Bureau  of  Entomology  were  carried 
out  in  this  case  resulted  in  bringing  the  beetle  under  complete  control. 
Only  7  trees  had  been  successfully  attacked  by  the  beetles  which  had 
emerged  from  some  400  infested  trees  which  were  not  cut  during  the 
previous  control  operations.  Over  100  trees  were  found  that  had 
been  attacked  by  the  beetles,  but,  owing  to  the  limited  number  of 
the  latter,  the  trees  were  able  to  resist  them  and  recover. 

It  is  now  evident  that  the  control  operations  carried  on  in  southern 
Colorado  during  the  past  three  years,  on  the  Trinchera  estate  near 
Fort  Garland  in  1906,  in  the  Las  Animas  National  Forest  and  Wet 
Mountains  section  of  the  San  Isabel  National  Forest  in  1908,  and 
the  more  extensive  work  in  the  latter  area  in  1909,  had  a  far-reaching 
effect  in  bringing  the  Black  Hills  beetle  under  control  within  the 
forested  areas  of  southern  Colorado,  and  that  the  loss  of  timber 

[Cir.  125] 


8  INSECTS    WHICH   KILL  FOREST    TREES, 

from  this  source,  amounting  to  an  average  of  bome  300,000  board  feet 
annually,  has  been  reduced  to  a  minimum. 

These  results  mark  the  most  important  events  in  the  control  of 
forest  insects  in  this  country-  and  serve  as  striking  demonstrations  of 
what  can  be  accomplished  when  cooperative  efforts  are  directed  along 
the  proper  lines  and  based  on  the  results  of  scientific  investigation. 
The  attainment  of  these  results  was  due  to  three  important  factors: 
First,  a  knowledge  of  the  insects  on  which  the  recommendations  by 
the  Bureau  of  Entomology  were  based :  second,  a  knowledge  of  local 
conditions  and  requirements  and  of  the  habits  of  the  insects  in  rela- 
tion to  newly  infested  trees,  which  enabled  a  forest  ranger  to  locate 
the  infested  trees  and  give  instructions  to  the  forest  officials  in  regard 
to  such  locations  and  the  essential  details  in  the  recommendations; 
third,  a  prompt  and  proper  practical  application  by  the  Forest  Serv- 
ice of  the  recommendations  according  to  improved  forestry  methods 
to  meet  the  requirements  of  a  forestry  problem. 

Ten  years  ago  it  would  have  been  absolutely  impossible  to  have 
accomplished  this  result,  owing  to  the  utter  lack  of  knowledge  of  the 
first  two  of  these  features,  and  at  the  present  time  it  would  have 
been  impossible  without  the  assistance  of  the  Forest  Service. 

CONTROL    OF    THE    MOUNTAIN    PINK    BEETLE. 

A  very  threatening  outbreak  of  the  mountain  pine  beetle  was  lo- 
cated, in  1909.  in  the  Snowy  Mountains  section  of  Montana,  adjacent 
to  and  within  the  Jefferson  National  Forest,  involving,  at  the  time, 
more  than  1.500  infested  and  dying  trees.  The  infestation  included 
timber  on  the  National  Forest,  public  domain,  state  lands,  and  private 
lands,  thus  involving  a  complication  of  federal,  state,  and  private 
interests  with  which  to  deal  in  securing  the  required  action.  The 
case  was  so  successfully  managed  that  an  agent  of  the  Bureau.  Mr. 
Josef  Brunner.  was  placed  in  complete  charge  to  carry  out  the  recom- 
mendations and  instructions  of  this  Bureau,  and.  through  the  aid  of 
the  Forest  Service,  state  officials,  and  private  owners,  1.3r).5  infested 
trees  were  cut  and  barked  to  kill  the  broods  of  beetles.  The  cutting 
was  started  about  June  15,  1909.  and  was  completed  about  July  24 
of  the  same  year.  Four  hundred  and  twenty-two  trees  were  cut  at 
private  expense,  783  at  the  expense  of  the  Forest  Service,  and  the  re- 
mainder by  local  owners.  Tlie  average  cost  for  felling  and  removing 
the  bark  from  the  infested  portion  of  the  trunk  was  30  cents  per  tree. 

Early  in  December,  1909,  a  careful  examination  was  made  of  the 
area  for  evidence  of  new  infestation.  It  was  found  that,  while  some 
5G  trees  had  bei'n  attacked  by  the  mountain  pine  beetle,  the  broods 
were  being  destroyed  by  woodpeckers  and  other  natural  enemies,  and 
that,  therefore,  the  efforts  to  control  the  beetle  depreilations  were  a 
complete  success. 


INSECTS    WHICH    KILL   FOREST   TREES.  9 

The  examples  of  practical  control  given  above  have  demonstrated  at 
least  two  important  facts :  One,  that  extensive  outbreaks  by  two  of  the 
most  destructive  bark-beetle  enemies  of  the  pine  timber  of  the  Rocky 
Mountain  forests  can  be  controlled  at  moderate  expense  when  the  tim- 
ber is  not  accessible  for  utilization,  or  at  a  profit  whenever  the  condi- 
tions are  favorable  for  the  utilization  of  the  infested  timber ;  the  other, 
that  the  essential  details  of  the  recommendations  and  expert  advice, 
based  on  the  results  of  scientific  research,  can  be  successfully  applied  by 
a  manager  of  a  private  forest  or  by  the  rangers  of  national  and  state 
forests.  Furthermore,  these  results  indicate  quite  conclusively  that 
the  widespread  depredations  in  the  Black  Hills  Xational  Forest  could 
have  been  prevented  with  very  little  expense  to  the  Government  if  the 
matter  had  received  prompt  attention  in  1901,  when  the  first  investi- 
gations were  made  and  essentially  the  same  recommendations  sub- 
mitted as  in  the  cases  mentioned.  Failure  to  do  so  was  through  the 
lack  of  public  appreciation  of  the  importance  of  the  problem  at  the 
time  and  the  lack  of  sufficient  authority  and  funds  later.  Therefore 
the  outbreak  was  allowed  to  extend  beyond  practical  control,  and  in 
consequence  a  large  percentage  of  the  timber  of  the  entire  Xational 
Forest  has  been  killed.  There  were  then  no  forcible  examples  of  the 
practical  value  of  recommendations  based  on  scientific  research,  and 
no  other  argument  was  effective  in  arousing  public  interest  in  the 
threatening  character  of  the  outbreak  or  confidence  in  the  advice  and 
methods  of  control.  Now  that  the  practicability  of  controlling  the 
most  destructive  insect  enemies  of  North  American  forests  has  been 
demonstrated,  this  should  lead  to  a  more  general  interest  in  the  subject 
and  confidence  in  the  results  of  scientific  research  as  a  basis  for  success 
in  practical  application. 

Approved : 

James  Wilson, 

Secretary  of  Agmculture. 
Washington.  D.  C,  October  7, 1910. 

64136  =  — 10 

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